This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Here we propose to use the NCXT beamline to study morphological changes of a strain engineered to be enriched in old Saccharomyces cerevisiae cells. This study will provide a first comprehensive view of the morphological phenotypes of aging in yeast. We propose to examine the morphology of the parent and daughter arrester strains in both in the presence and absence of an inhibitory compound. While the introduction of the daughter arrester gene or presence of drug does not significantly affect the cell cycle length relative to the parent strain in the absence of drug, it is possible that either change could cause subtle morphology alterations. We propose to use soft X-ray tomography to quantitatively compare the yeast cell morphologies of these strains under these different conditions to detect such changes.